Precise metering of lubricant dispensing is required in order to ensure both economical and sufficient lubrication. If lubricant is dispensed at excessively short intervals or in excessively large quantities, too much lubricant is used and the lubricant cartridge must be replaced earlier than necessary. Conversely, deficient lubrication occurring due to dispensing lubricant in too small amounts or too infrequently often results in damage to the machine components to be lubricated.
In order to determine the quantity of delivered lubricant, the current art estimates the quantity of gas generated by the gas-generating cell. This approach exploits the fact that under typical conditions the quantity of gas delivered by an electrochemical gas-generating cell is roughly proportional to the amount of current flowing through the gas-generating cell. Since the voltage that is produced by the chemical potential in a gas-generating cell, or the supply voltage from a DC voltage source that is possibly used to supplement this, and also the electrical properties of the gas-generating cell, such as, for example, the internal resistance are all known, the amount of current can be estimated that has flowed during the time the circuit is closed. The dispensing duration is defined based on this calculation and used as a fixed default value.
Practical experience has revealed, however, that the electrical properties of the circuit are variable. In particular, they change over the service life and performance life of the gas-generating cell and of any voltage source. They are furthermore highly temperature-dependent. The geometry of different cartridges with varying initial volumes of lubricant also affects the quantity of lubricant that is actually delivered. These effects mean that the above-described estimate of a delivered metered quantity of lubricant is increasingly imprecise, and the use of default values for the dispensing duration produces unsatisfactory results.